25.4 Testing and characterization of integrated systems

Integrated energy harvesting systems need rigorous testing to ensure they perform as intended. This section covers key performance metrics, characterization techniques, and environmental stress tests used to evaluate these systems.

Reliability and longevity are crucial for energy harvesters in real-world applications. We'll explore methods for assessing system lifespan, identifying failure modes, and conducting root cause analysis to improve design and performance.

Performance Evaluation

Power Output and Efficiency Metrics

• Power output measurement quantifies energy harvested by integrated system
• Efficiency evaluation compares actual output to theoretical maximum
• Performance metrics include open-circuit voltage, short-circuit current, and maximum power point
• Power density calculation determines energy harvested per unit area or volume
• Conversion efficiency assesses percentage of input energy converted to usable electrical output

System Response Characterization

• Frequency response analysis examines system behavior across different vibration frequencies
• Bandwidth measurement determines operational frequency range of energy harvester
• Resonant frequency identification optimizes energy harvesting performance
• Time-domain analysis evaluates transient response and settling time of system
• Load resistance optimization maximizes power transfer to connected electrical load

Advanced Performance Analysis Techniques

• Impedance matching ensures maximum power transfer between harvester and load
• Power management circuit evaluation assesses efficiency of energy storage and conversion
• Multi-axis testing examines harvester performance under complex vibration patterns
• Temperature coefficient analysis determines impact of temperature variations on output
• Fatigue testing evaluates long-term performance under repeated stress cycles

Environmental and Reliability Testing

Environmental Stress Testing

• Temperature cycling subjects system to extreme hot and cold conditions (−40°C to 85°C)
• Humidity testing evaluates performance in high moisture environments (up to 95% relative humidity)
• Vibration testing assesses durability under various vibration profiles (sinusoidal, random, shock)
• Altitude testing examines operation at different atmospheric pressures
• Salt spray testing evaluates corrosion resistance in marine or coastal environments

Reliability and Longevity Assessment

• Accelerated life testing estimates system lifespan under accelerated stress conditions
• Mean Time Between Failures (MTBF) calculation predicts average time between system failures
• Weibull analysis characterizes failure rates and identifies wear-out periods
• Thermal shock testing evaluates system response to rapid temperature changes
• Mechanical shock testing assesses resilience to sudden impacts or drops

Failure Mode and Root Cause Analysis

• Failure Mode and Effects Analysis (FMEA) identifies potential failure modes and their impacts
• Root Cause Analysis (RCA) determines underlying causes of system failures
• Non-destructive testing techniques (X-ray, ultrasound) inspect internal components without damage
• Destructive physical analysis examines failed components through controlled disassembly
• Statistical process control monitors manufacturing variability to prevent systemic failures